(a) Field of the Invention
The present invention relates to a photovoltaic device. More particularly, the present invention relates to a photovoltaic device that can improve efficiency by forming an organic buffer layer.
(b) Description of the Related Art
Photovoltaic devices that convert light signals into electrical signals can be applied to diverse fields such as sensors and solar batteries.
Since the photovoltaic devices are environment-friendly and have many advantages such as an infinite energy source and long life-span, many researchers are studying about the photovoltaic devices. However, since the photovoltaic devices are limited in improving their efficiency, they have been difficult to commercialize.
Diverse methods have been suggested to improve the photovoltaic efficiency. Among them is a method of forming a buffer layer of an inorganic chemical compound in a photovoltaic device.
However, buffer layers suggested so far have a problem in that they improve the photovoltaic efficiency not sufficiently and the formation of the buffer layers requires strict conditions.
To take an example, there is a method of forming a buffer layer of LiF, which is an inorganic compound, in an organic solar cell. Since LiF is a non-electric conductor, a thick LiF buffer layer rather decreases the photovoltaic efficiency of the organic solar cell.
Buffer layers should be formed thinner than 10 Å to improve the photovoltaic efficiency. When a thickness of a buffer layer is thicker than 10 Å by even a few Å, the efficiency of an organic solar cell is deteriorated.
However, it is substantially difficult to form a buffer layer uniformly in the thickness, and process conditions should be controlled strictly to form the uniform buffer layer thinner than 10 Å.
It is particularly difficult to form a buffer layer in a wide area if the buffer layer is less than 10 Å. Therefore, there is a problem in that the buffer layer is difficult to apply to a large-area organic solar cell.
In addition, since it is substantially difficult to form the buffer layer in a uniform thickness, there is a problem in that a buffer layer of an uneven thickness may lead to uneven efficiency of the photovoltaic device.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.